As a legislative branch agency, the Capitol Police force is subject to oversight by both chambers of Congress, the Government Accountability Office, the Office of Compliance and other external entities, including an independent Office of the Inspector General.

The department also holds itself to more than 350 meticulous standards set by the Commission on Accreditation for Law Enforcement Agencies Inc., better known as the CALEA. The nonprofit corporation was established in 1979, through joint efforts of major law enforcement groups such as the International Association of Chiefs of Police and the National Sheriffs' Association as part of a movement to bring more professionalism to policing.

For more than 13 years, Capitol Police have maintained CALEA accreditation, paying around $100,000 in fees. On Nov. 22, the department's accreditation will be up for its latest review. To earn accreditation, law enforcement agencies must prove they comply with CALEA standards covering a broad range of issues. Capitol Police provided a printed copy of the standards to CQ Roll Call — four manila envelopes stuffed with hundreds of pages of rules on everything from use of force and bias-based profiling, to employment conditions and ethics.

Accreditation comes with perks, such as reduced liability insurance rates. It is also one of the best defenses against lawsuits. In the past year, the department has been threatened with a wrongful death lawsuit from the family of Miriam Carey, the woman shot outside the Capitol on Oct. 3, 2013, after an erratic car chase from the White House. For more than a decade , a group of black officers have been waging a legal battle against Capitol Police, alleging discrimination.

"In the event that the civil litigation arises, they're prepared," W. Craig Hartley Jr., executive director of CALEA, said in a phone interview from his Virginia-based office. When a department is sued, the lawsuit can also have bearing on the accreditation status, though Hartley emphasized the CALEA certification is about "continuous improvement" and developing strategies to bring agencies into compliance, not punishment for falling short.

Accreditation also comes with costs. Departments with more than 1,000 full time employees pay a lump sum of $18,600 in initial accreditation fees, according to CALEA, but the commission reserves the right to make "special adjustments" for some agencies.

Capitol Police voluntarily sought accreditation in 1999 under the leadership of then-Chief Gary L. Abrecht, who served at the helm of the force from 1992 to 2000. The department received its initial award in 2002. At the time, Congress and other entities were scrutinizing management of the Capitol Police. After a gunman killed two officers inside the Capitol during a 1998 shooting, the department undertook a plan to beef up security by hiring additional officers and upgrading weapons and body armor. A January 1999 study by Booz Allen Hamilton recommended an administrative overhaul, including budgeting and human resources.

To maintain accreditation, large departments such as the Capitol Police pay at least $5,765 in annual continuation fees. The department employs two "accreditation managers," serving as sticklers for the rules. Capitol Police must undergo re-accreditation every three years, a process that involves an on-site assessment. The cost of that visit varies based on lodging, airfare and other factors specifically related to the department, according to CALEA.

For four days in mid-August, Capitol Police hosted a two-person assessment team who reviewed written reports, conducted interviews and visited police facilities. One was a police chief from Maine, the other an inspector from Georgia. Capitol Police declined to provide information on the cost of this year's visit.

Those two assessors will report back to the full commission, which will make its determination during the Nov. 22 meeting.

Correction 4:35 p.m. An earlier version of this article misstated the year that Capitol Police received its initial award due to an error on the CALEA site.